Magnetization measurements in the low field region have been carefully
performed on a well-shaped cylindrical and an ellipsoidal sample of
superconductor MgCNi3​. Data from both samples show almost the same results.
The lower critical field Hc1​ and the London penetration depth λ
are thus derived. It is found that the result of normalized superfluid density
λ2(0)/λ2(T) of MgCNi3​ can be well described by BCS
prediction with the expectation for an isotropic s-wave superconductivity.Comment: To appear in Phys. Rev.